Q&A: Do your soil tests represent your fields?

Recent developments in soil testing, plus challenges to longstanding tests raise the question, how confident are farmers that their soil tests represent their fields? Three farmers share their takes:

Jim Darnell, Scottsbluff, Neb.

My fertilizer company does my soil testing. I’ve been with them about 35 years so we’ve built up a mutual trust. I rely on them to follow all the recommendations for soil sampling. I do also talk with Gary Hergert, a soils expert from the University of Nebraska. Sometimes I’ve taken the soil tests to Gary, and we’d sit down and go over them. We’d talk about the results, and also about how and when to apply the fertilizer.

We’re all irrigated here.

We take random samples, testing every field at least every 3 years. Some people geo-reference their soil samples, and that looks like a good idea that I might try.

I did some grid sampling about 10 years ago, and then tried variable-rate fertilizer following the recommendations. But the extra cost for that wasn’t justified in any yield increases, so I stopped doing that.

Philip Krumm, Center Point, Iowa

You get to know your own ground pretty well after you farm it for years, so the soil test is a back-up and a confirmation for your own feelings in many cases. I’ve been soil testing every 2 to 3 years and more often than that if there’s an issue.

I just had some samples taken last fall, and I watched them take the samples. They don’t use GPS, but they know the farm and they won’t mix in samples from a sandy spot or from an old building site.

I’ve worked with the same retailer for 40 years, a family-owned elevator. They spread the fertilizer, too, and know the farm like I do. I’m confident we’re not over-applying based on soil tests and removal rates.

I’ve learned over the years that you have to trust somebody, and I trust them. It’s really pretty simple for me.

Tom Lutz, Wenona, Ill.

I used to take 8 samples on an 80-acre field, but now I’ve tripled the number of samples for more accuracy. I don’t have a lot of variation in my soils—I’ve only got three major soil types on the farm.

I like to keep my farming simple. But if I see a small area from the soil tests or the combine monitor that shows a need, we’ll try to map it out and pop more potash or phosphorus or whatever’s indicated on that area.

My soil testing and fertilizer application come from a local fertilizer co-op. I’m confident the man I work with there is taking enough samples from the right locations in the fields. He’s a farmer, too, and we can talk things over. We’re long-time customers—I’ve worked with him long enough to know he doesn’t try to push more fertilizer on anyone than is needed.